Feedback cooling of a room temperature mechanical oscillator close to its motional groundstate

TL;DR

This paper demonstrates feedback cooling of a room temperature mechanical oscillator to near its motional ground state using integrated nanophotonics and phononic band gap engineering, advancing room temperature quantum optomechanics.

Contribution

It introduces a novel microchip technology that achieves high cooperativity and effective feedback cooling from room temperature, approaching the quantum ground state.

Findings

Achieved a single-photon cooperativity of 200.

Successfully cooled a mechanical resonator to around 1 mK from room temperature.

Demonstrated a significant step towards room temperature quantum optomechanics.

Abstract

Preparing mechanical systems in their lowest possible entropy state, the quantum ground state, starting from a room temperature environment is a key challenge in quantum optomechanics. This would not only enable creating quantum states of truly macroscopic systems, but at the same time also lay the groundwork for a new generation of quantum-limited mechanical sensors in ambient environments. Laser cooling of optomechanical devices using the radiation pressure force combined with cryogenic precooling has been successful at demonstrating ground state preparation of various devices, while a similar demonstration starting from a room temperature environment remains an outstanding goal. Here, we combine integrated nanophotonics with phononic band gap engineering to simultaneously overcome prior limitations in the isolation from the surrounding environment and the achievable mechanical frequencies, as well as limited optomechanical coupling strength, demonstrating a single-photon cooperativity of 200. This new microchip technology allows us to feedback cool a mechanical resonator to around 1 mK, near its motional ground state, from room temperature. Our experiment marks a major step toward accessible, widespread quantum technologies with mechanical resonators.